Ocular Trauma Causes and Effects

Ocular trauma is a debilitating condition and is emerging as a leading cause of blindness. Ocular trauma remains challenging not only for ophthalmologists but also for emergency physician, anaesthesiologist and intensivist. The appropriate and timely assessment of ocular trauma in emergency care settings may provide good outcome. Anaesthetic implications include timing of the surgical intervention, interaction of various anaesthetic and ophthalmic drugs and airway management techniques. The concern like sympathetic ophthalmia is also a major issue relating to ocular morbidity after ocular trauma.

INTRODUCTION

Ocular trauma has emerged as a leading cause of blindness with an annual incidence for more than a million cases of bilateral blindness and 500,000 cases of unilateral blindness with children comprising 8-14% of all ocular injuries.^1,2,3,4 The management of trauma remains quite challenging not only for ophthalmologists but also for anaesthesiologists, emergency care physicians and intensivist. The ocular injury has significant long term impact on the individual and the society. Ocular injury have debilitating effects on quality of life and may be considered as severe as limb-threatening injuries.⁵ All patients with craniofacial or midfacial, injuries should be examined for ocular injuries apart from traumatic brain injury.¹

TYPES OF INJURY

Ocular trauma is frequently associated with facial trauma specially to upper face and forehead.⁶ The lesser protected orbital structures from bony orbit predisposes to the eye injuries.⁵ Ocular trauma have a wide variety of presentation ranging from corneal epithelial abrasion to the more severe pen­etrating and globe rupture injuries.^1,7,8 The commoner injuries include injury to eyelid, cornea, anterior chamber, iris, lens, retina, globe, fractures, vitreous haemorrhage, retrobulbar haematoma and fat emboli. The mechanism of ocular trauma may be mechanical (penetrating, contusion, foreign body), chemical, thermal or may be combination of either of these.8 Gun shot or other high speed projectiles may cause variable trauma to the ocular structures.⁸ The presence of broken glass, wood, or metal fragments at the scene should prompt the suspicion of penetrating injuries.⁵ The thin bony structures may lead to ocular injuries in patients with craniofacial injuries and intracranial injuries in patients with penetrating orbital injuries.⁵

Chemical injuries accounts about 10% of all ocular injuries.⁵ Alkalis are more damaging than the acid solution to the eye because of their deeper penetration. The commonest cause is domestic and industrial accidents and assault.⁵ These patients should receive local anaesthetic drops, pH evaluation and irrigation with copious amounts of Ringer lactate, started immediately in the emergency care area itself.⁵ Further management requires specialist ophthalmic care.

INCIDENCE & EPIDEMIOLOGY

The life time prevalence of ocular injury is reported variably ranging as 4.5- 21.1%.^9-11 The major cause of ocular injuries are accidental but may also be associated with assaults; accidental ocular injuries being more common in children while intentional assaults are commoner in adults.^8,12 In a Delhi based study, ocular trauma was more commoner at work and home, and blunt trauma was commoner than penetrating ocular trauma.¹¹ The male: female ratio has been reported ranging from 3:1 to 5.4:1 worldwide while in India it estimates at 2.4:1.^12-15 The ocular injury is more common at a younger age.^{7,10,12,16,17} In a study which included 166 patients with ocular injury, 77.11% were below 35 years of age.¹² Among these, 43.3.7% were between 26 – 35 years of age and 33.74% between 16 –25 years. Among the paediatric age group, 61.28% of ocular trauma was reported to be in children aged 1-10years.¹⁸ The ocular injury is more commoner in left eye as compared to right eye with bilateral injury being the least as compared to unilateral injury.^12,19,20 The ocular injury has been correlated with increased incidence of repeat injury threefold as compared to patients without history of ocular trauma.7 Over 90 % of these injuries are preventable and morbidity may be decreased by either suitable preventive measures or by optimal assessment and intervention in cases of ocular trauma.^1,6,12

INITIAL ASSESSMENT

The initial assessment with regards to ocular injury in trauma victim needs to be done with a systematic approach.²¹ The ocular examination needs to be done in conjunction with the head to toe examination once life threatening injuries have been dealt with as per the trauma management principles.²¹ The ocular assessment includes patient history, history of the injury incident, initial symptoms and physical examination.²¹ The history needs to include any preexisting ocular disease or use of any ocular drug.²¹ Details of incident may be helpful for suspicion of any other associated injury, the type of ocular injury and possibility of infection. The physical examination includes anatomic as well as functional evaluation including assessment of visual acuity, papillary condition and function, motility of the eye, and intraocular pressure. The trauma victims with eye injury require evaluation of the anterior and posterior segment evaluation using a slit lamp or handheld lens and opthalmoscope. The systemic approach for ocular examination may be directed in an “outside-to inside” manner, thus avoiding any missed injury.²¹ These assessment parameters related to eye may be done in conjunction with the ophthalmologists and may prove to be useful in planning the anaesthetic technique so as to have good ocular outcome. Assessment may be repeated depending upon any change in patient’s clinical status with an aim to prioritize overall patient care.⁵ During assessment itself, patient may be administered antiemetics such as metoclopramide, serotonin antagonists, or promethazine to prevent vomiting induced increase in intraocular pressure (IOP).

Preanaesthetic work up remains the same as for other surgical procedure with rider of time limiting factor for trauma victims.²² The preoperative anaesthetic assessment may be done with thorough history and physical examination. This may give us a clue for further assessment or selection of preoperative laboratory tests.^22,23 The role of laboratory investigations may be limited due to time constraint in trauma victims. But if time permits, routine investigations are desirable. Specific investigations based on history and physical examination may be done.

Ultrasound has emerged as an important screening and diagnostic modality for detection of injuries in a trauma patient.^25-28 It is considered to be a fast and accurate examination tool with a fast learning curve.²⁵ Ultrasound has been conventionally used by ophthalmologist for eye evaluation. But recently its role in trauma patients by non-ophthalmologists has been emphasized. Eye being superficial organ and filled with fluid like structures allows for detection of trauma like retinal detachment, vitreous haemorrhage, foreign bodies using a high-frequency transducer.²⁶ Also, ultrasonography may be used for repeat examination during follow up for any change in finding with any adverse effect to the eye.²⁶ It also helps in ocular evaluation in trauma patients with significant orbital or facial swelling as physical examination or other conventional techniques may not be feasible for ocular examination due to inability to open the eyelid.²⁵. Ultrasound is also helpful for examining the pupillary response and its size in trauma victims with possible central nervous system injuries or concerns with autonomic nervous system due to trauma.^25-27

TIMING OF OPHTHALMIC SURGICAL INTERVENTIONS:

The ocular trauma is usually attended once life threatening clinical conditions has been managed or in other words timing of surgery depends on the general condition of the patient and the presence of other injuries. In case of unstable clinical conditions, the eye surgery may be delayed inspite of the ophthalmologic imperative or likely visual prognosis. On the other hand, patients without life-threatening or other major trauma, the timing of ophthalmologic intervention may be assessed by the need for urgent versus delayed surgery and visual prognosis based on ophthalmologist evaluation. Majority of ocular trauma do not require emergent intervention and the patient may be evaluated and optimized prior to intervention.²⁹ Delaying surgery for gastric emptying to occur is not reliable, as gastric emptying may be prolonged in this stressful situation.²⁹ The true emergencies includes chemical burns of the cornea and central retinal artery occlusion and needs to be managed emergently with the initiation of therapy within minutes. The injuries like open-globe injuries, endophthalmitis, acute retinal detachment, corneal foreign body, and lid laceration are considered urgent ophthalmologic conditions and therapy needs to be started within 1 to several hours without having any impact on ocular outcome.¹ The semi-urgent ocular injuries include blow-out fractures of the orbit and may be managed within days to weeks. However, in case of delay in ocular intervention for injured eye due to other trauma priorities, supportive care may be continued. This includes eye irrigation with saline, antibiotic coverage, artificial tears, sterile dressings and/or adequate corneal cover using traction sutures.¹ In cases where the patient has been anaesthetized for any other non-ocular surgical procedure, the ophthalmologist may choose to treat the eye injuries.

SPECIFIC CONCERNS WITH OCULAR TRAUMA AND PERIOPERATIVE CARE

The eye injury management has certain peculiar issues related to eye like oculocardiac reflex, use of drugs and impact of various interventions on intraocular pressure (IOP) which may impact the outcome of the injury to the eye.

The Oculocardiac Reflex

The oculocardiac reflex (OCR) is a trigeminovagal response which is elicited by the pressure on the globe, orbital contents or traction on the extraocular muscles.^23,24,30 The path of reflex includes stimulus passing through ciliary ganglion and further on to ophthalmic division of the trigeminal nerve and finally to sensory nucleus of the trigeminal. Efferent of the reflex arc is via vagus nerve. It leads to cardiac dysrhythmias like bradycardia, atrioventricular block, ventricular ectopy, or asystole.²² This reflex has also been seen with orbital injections and is exacerbated by hypercapnia or hypoxemia. This may be of concern in polytrauma patients as associated injuries may have impact on ventilation. The volatile agents like sevoflurane has more protective affect on OCR as compared to halothane.^22,23 The lighter plane of anaesthesia increases the possibility of the OCR as compared to deeper plane of anaesthesia .²³ The OCR is more commonly seen with rocuronium as compared to atracurium.^22,31 The OCR has also been associated with increased chances of postoperative nausea and vomiting (PONV) and somnolence.³² The reflex is usually attenuated with repeated stimulus and routine prophylaxis is controversial with a favour toward not administering prophylactically. The management includes stoppage of surgical manipulations, optimization of respiratory status and depth of anaesthesia, and in case of persistence or recurrence of OCR, anticholinergic medication like atropine or glycopyrolate is often helpful.³³ Also, the topical local anaesthetic agents and peribulbar block may attenuate the occurrence of OCR by blocking the afferent limb of the reflex.^34,35 In trauma patient, OCR may be mimicked by bradycardia due to significant intracranial injury leading to raised intracranial pressures.^36,37 Rarely, the orbital wall fractures, more commonly described with trapdoor than comminuted fractures, may lead to potentially life-threatening oculocardiac reflex.^36,37 Thus, it becomes prudent to aware that the oculocardiac reflex might mimic signs of intracranial hypertension in patients with combined facial and cerebral trauma.^36,37

Intraocular Pressure

The intraocular pressure (IOP) is affected with various perioperative physical, physiological and pharmacological components.^22,38,39,40 The factors like laryngoscopy, intubation, coughing, straining, crying, bucking, vomiting reflex, hypoxia and hypercapnia lead to increase in IOP.^22,41-44 Any compromise of venous return may decrease aqueous humor drainage and thus may lead to increased volume of choroidal blood leading to increased IOP. While on the other hand, hypocapnia, hypothermia and most anaesthetic agents decreases IOP.^23,24,30 The increase in IOP may be attenuated by administration of intravenous lidocaine (1 mg/kg) prior to inciting factor.²² Also, the airway management technique can be suitably chosen like laryngeal mask airway (LMA), which has lesser impact on IOP as compared to the use of tracheal tube.^22,45,46,47 The drugs like ketamine and succinylcholine may transiently increase the IOP while volatile anaesthetics or thiopental anaesthesia causes a dose-related reduction in IOP.^38,48,49 The IOP reduction has been reported to be proportional to the depth of anaesthesia.³⁸ Nondepolarizing muscle relaxants do not increase IOP.^50,51 Opioids and atropine in the usual doses have little effect on IOP.^24,38

The blood supply of the eye depends on the intraocular perfusion pressure which is dependent on mean arterial pressure and the IOP. Both these pressures may be affected in polytrauma patients where mean arterial pressure may fall due to blood loss and IOP may rise due to ocular injury. This may severely compromise the ocular blood perfusion. The optimization of blood supply in polytrauma patients needs to be done so as to maintain optimal physiological status and thereby intraocular perfusion pressure. The factors that may decrease local ocular blood supply like extrinsic compression by anaesthesia face mask should be avoided.^41-44